1. Field of the Invention
The present invention relates to a seal structure of a steam passage between a blade ring and a stationary blade of a steam cooled type gas turbine, that is so structured that cooling steam, flowing in a cooling steam supply passage and return passage, is prevented from leaking from a steam shield connection portion of the blade ring and a fitting portion of the stationary blade.
2. Description of the Prior Art
The recent combined cycle power plant (herein simply referred to as xe2x80x9cthe plantxe2x80x9d) is in the tendency that a gas turbine thereof is operated at a higher temperature for realizing a higher efficiency of the plant and, in order to improve the thermal efficiency, such a gas turbine as uses steam, instead of air, as cooling medium for cooling a gas turbine blade and the like is being developed.
In such a steam cooled type gas turbine, the steam for cooling the gas turbine blade and the like, flowing in a seal structure of a steam passage between a blade ring and a stationary blade (herein simply referred to as xe2x80x9cthe seal structurexe2x80x9d), is not discharged into main flow gas as combustion gas but cooling heat of the gas turbine blade and the like is recovered into a steam turbine of the plant, thereby increasing output of the entire plant. Also, by suppressing blowing quantity of the cooling medium into the combustion gas that drives the gas turbine blade, temperature lowering of the combustion gas is prevented and the gas turbine efficiency is enhanced and thus the efficiency of the entire plant can be enhanced.
In the plant described above, the cooling steam used as the cooling medium is usually of a pressure higher than the atmospheric pressure and needs to be shielded against the atmospheric pressure to be supplied into the gas turbine interior.
Also, in order to enhance the output of the entire plant by recovering the cooling steam into the steam turbine, it is necessary to make cooling steam passages, provided in the outer and inner blade rings and the stationary blade of the gas turbine, in a closed form.
A prior art seal structure made in such a closed form will be described with reference to an example shown in FIG. 7. While this example has been originally designed to use compressed air as cooling medium, it is modified so as to use cooling steam for cooling the steam cooled type gas turbine.
As used herein, the term xe2x80x9couter, or inner, circumferential sidexe2x80x9d means the outer, or inner, circumferential side in a rotor radial direction of the gas turbine or, in other words, xe2x80x9cthe upper, or lower, sidexe2x80x9d as seen in the respective figures appended herein.
As shown in FIG. 7, in the prior art seal structure, cooling steam is supplied from outside (not shown) into a blade ring 10 to flow through a steam shield connection portion 21 and a blade ring cooling steam supply passage 30, that is provided in the blade ring 10, and cools the blade ring 10. Then, the cooling steam flows through a seal pipe 25 to enter a stationary blade 50. The seal pipe 25 is of a hollow cylindrical shape having at one end a flange portion 26 and is provided in a cooling steam supply passage connection portion between the blade ring cooling steam supply passage 30 and a stationary blade cooling steam supply passage 39, that is provided in the stationary blade 50. While flowing through the stationary blade cooling steam supply passage 39, the cooling steam cools the stationary blade 50 and, having been used for the cooling, it is recovered outside of the blade ring 10 through a cooling steam return passage (not shown), that is provided to pass through the blade ring 10.
When the cooling steam enters the steam shield connection portion 21, it is of a temperature of about 200 to 300xc2x0 C. and when the cooling steam returns to the cooling steam return passage, it is heated to a temperature of about 500 to 600xc2x0 C., that is elevated by cooling the blade ring 10 and the stationary blade 50.
Thus, in the portions through which the cooling steam flows, there are caused thermal deformations in the rotor axial, radial and circumferential directions by the heat of the steam and it is needed to provide there such a steam passage seal structure that is able to absorb the thermal deformations. That is, the prior art seal structure, as shown in FIG. 7, is made such that, in a fitting portion of the stationary blade 50 to the blade ring 10, the blade ring cooling steam supply passage 30 and the stationary blade cooling steam supply passage 39 are connected together at a shroud 42, that is provided around a periphery of the fitting portion of the stationary blade 50 and is fastened by a bolt 41. Thereby, a seal is effected at the flange portion 26 by a metal seal ring 70axe2x80x2, 70bxe2x80x2 but, in this seal structure, there is still a problem that minute gaps arise in the cooling steam supply passage connection portion due to the thermal deformation to cause a steam leakage.
In order to solve the problem in the prior art to cause the steam leakage at the connection portion between the blade ring cooling steam supply passage and the stationary blade cooling steam supply passage, it is an object of the present invention to provide a seal structure of a cooling steam supply passage connection portion between a blade ring and a stationary blade of a steam cooled type gas turbine that is able to greatly enhance the sealing ability and to largely advance the realizability of a steam cooled blade ring and stationary blade. In addition to this, it is also an object of the present invention to provide a like seal structure of a cooling steam return passage provided in the blade ring and the stationary blade.
In order to achieve the mentioned objects, the present invention provides the means of the following inventions (1) to (13), wherein the inventions (2) to (13) are based on the invention (1), and functions and effects of the respective inventions (1) to (13) will be described in items (a) to (m).
(1) As a first one of the present invention, a gas turbine steam passage seal structure between a blade ring and a stationary blade, comprises: a blade ring steam passage hole provided in the blade ring so as to have its one end communicated with a steam passage chamber of the blade ring, the blade ring steam passage hole having a stepped portion formed in a middle portion thereof; a stationary blade steam passage hole provided in the stationary blade so as to oppose the other end of the blade ring steam passage hole, the stationary blade steam passage hole having a stepped portion formed in a stationary blade outer peripheral portion thereof; and a cooling steam supply passage connection portion constructed comprising a seal pipe of a hollow cylindrical shape provided between the blade ring steam passage hole and the stationary blade steam passage hole so as to communicate them with each other and a seal urging guide device provided at each of the stepped portions of the blade ring steam passage hole and the stationary blade steam passage hole so as to effect a seal of the cooling steam supply passage connection portion while fixedly supporting the seal pipe.
(a) By the above construction, even if the blade ring and the stationary blade make deformations by the heat of the steam, the steam passages in the cooling steam supply passage connection portion between the blade ring and the stationary blade have a flexibility to elongate and contract in the rotor axial, radial and circumferential directions. Thereby, the deformations due to the heat of the steam are absorbed and also steam leakage through minute gaps in the cooling steam supply passage connection portion can be prevented so that drive force of the steam turbine using the recovery steam may be increased. Also, temperature lowering of the combustion gas due to the inflow of the leaking steam is avoided so that drive force of the gas turbine may be increased and the thermal efficiency of the combined cycle power generation plant can be improved.
(2) As a second one of the present invention, in addition to the means of the gas turbine steam passage seal structure of the invention (1) that is applied to a cooling steam supply passage, the same seal structure is also applied to a cooling steam return passage.
(b) By this construction, the same function and effect as in the above item (a) can be obtained, the drive force of the steam turbine as well as the drive force of the gas turbine are further enhanced and the thermal efficiency of the combined cycle power generation plant can be further improved.
(3) As a third one of the present invention, in addition to the means of the gas turbine steam passage seal structure of the invention (1), a metal seal ring is interposed between the seal urging guide device and at least one of the stepped portions of the blade ring steam passage hole and the stationary blade steam passage hole.
(c) By this construction, the same function and effect as in the above item (a) can be obtained and also the deformation caused in the blade ring and stationary blade cooling steam supply passages due to the heat of the steam can be absorbed by the deformation of the metal seal ring. Thus, the gaps caused in the cooling steam supply passage connection portion between the blade ring steam passage hole and the stationary blade steam passage hole can be substantially eliminated and steam leakage from these gaps can be prevented.
(4) As a fourth one of the present invention, in addition to the means of the gas turbine steam passage seal structure of the invention (1), the seal pipe has its lower end provided with a flange portion and the flange portion is fixedly supported to the stepped portion of the stationary blade steam passage hole by an urging force of the seal urging guide device provided in the stationary blade steam passage hole.
(d) By this construction, the same function and effect as in the above item (a) can be obtained and also the flange portion of the lower end of the seal pipe forming the blade ring cooling steam supply passage is fixedly supported by the urging force of the seal urging guide device provided in the stationary blade steam passage hole. Thus, leakage of the steam through gaps that may be caused by the thermal deformation or vibration in the blade ring and the stationary blade can be prevented.
(5) As a fifth one of the present invention, in addition to the means of the gas turbine steam passage seal structure of the invention (4), a gland packing case is fitted into the blade ring steam passage hole and a gland packing is interposed between the seal pipe and the gland packing case.
(e) By this construction, the same function and effect as in the above item (d) can be obtained and also the upper end portion of the seal pipe is fixedly supported by the pressing force of the gland packing of the seal urging guide device provided in the blade ring steam passage hole. Thus, gaps that may be caused by the thermal deformation or vibration around the outer peripheral portion of the seal pipe can be eliminated and steam leakage through these gaps can be prevented.
(6) As a sixth one of the present invention, in addition to the means of the gas turbine steam passage seal structure of the invention (1), the cooling steam supply passage connection portion is constructed comprising a first seal pipe provided between the blade ring steam passage hole and the stationary blade steam passage hole so as to communicate them with each other, a second seal pipe and a third seal pipe both provided in the blade ring steam passage hole and a fourth seal pipe provided in the stationary blade steam passage hole. The first seal pipe has at its outer circumferential upper and lower surfaces swell portions, the swell portion on the upper side making a slidable contact with an inner circumferential surface of the second seal pipe, the swell portion on the lower side making a slidable contact with an inner circumferential surface of the fourth seal pipe. The second seal pipe has on its outer circumferential surface a projecting portion that abuts on the stepped portion of the blade ring steam passage hole. The third seal pipe is supported at its outer circumferential surface to the blade ring steam passage hole via a screw engagement and makes at its inner circumferential surface a slidable contact with an outer circumferential surface of the second seal pipe, and the fourth seal pipe has at its lower end a flange portion.
(f) By this construction, the same function and effect as in the above item (a) can be obtained. Moreover, the entire seal structure is so made that assembly and disassembly of the seal pipes and the surrounding members for ensuring the sealing may be done easily.
(7) As a seventh one of the present invention, in addition to the means of the gas turbine steam passage seal structure of the invention (6), the second seal pipe has its upper inner circumferential surface provided with a tapered projecting portion so that the first seal pipe at its swell portion on the upper side may abut on the tapered projecting portion to be prevented from moving more upwardly.
(g) By this construction, the same function and effect as in the above item (f) can be obtained. Moreover, the tapered projecting portion of the second seal pipe prevents the first seal pipe from moving more upwardly to slip off beyond the second seal pipe. Thus, sealing between the first and second seal pipes can be ensured. If a metal coating is applied to the contact surfaces between the first and second seal pipes, friction there can be lessened and a more smooth slidable contact can be realized.
(8) As an eighth one of the present invention, in addition to the means of the gas turbine steam passage seal structure of the invention (6), the seal urging guide device of the blade ring steam passage hole is formed comprising the projecting portion of the second seal pipe that abuts on the stepped portion of the blade ring steam passage hole and the third seal pipe that is supported to the blade ring steam passage hole via the screw engagement so as to generate an urging force to press the second seal pipe downwardly.
(h) By this construction, the same function and effect as in the above item (f) can be obtained. Moreover, the upper outer peripheral portion of the cooling steam supply passage connection portion can be sufficiently sealed by the-urging force of the seal urging guide device of the blade ring steam passage hole. Thus, even if there are caused the thermal deformation and vibration in the seal pipes and the surrounding members, gaps through which the steam leaks are not caused and leaking steam can be greatly reduced.
(9) As a ninth one of the present invention, in addition to the means of the gas turbine steam passage seal structure of the invention (6), the seal urging guide device of the stationary blade steam passage hole is formed comprising the fourth seal pipe having the flange portion and a screw member as an independent member that is supported at its outer circumferential surface to the stationary blade steam passage hole via a screw engagement so as to generate an urging force to press the fourth seal pipe downwardly and makes at its inner circumferential surface a slidable contact with an outer circumferential surface of the fourth seal pipe.
(i) By this construction, the same function and effect as in the above item (f) can be obtained. Moreover, the lower end portion of the cooling steam supply passage connection portion can be sufficiently sealed by the urging force of the seal urging guide device of the stationary blade steam passage hole. Thus, even if there are caused the thermal deformation and vibration in the seal pipes and the surrounding members, gaps through which the steam leaks are not caused and leaking steam can be greatly reduced.
(10) As a tenth one of the present invention, in addition to the means of the gas turbine steam passage seal structure of the invention (1), the cooling steam supply passage connection portion at its portion provided in the blade ring steam passage hole is constructed comprising a bellows member that is elongatable and contractible in the rotor radial direction and a control ring that is fitted into a recessed portion of an outer periphery of the bellows member so as to stably support the bellows member.
(j) By this construction, the same function and effect as in the above item (a) can be obtained. Moreover, the cooling steam supply passage connection portion comprises the bellows member that is elongatable and contractible in the rotor radial direction. Thus, in operation of the gas turbine, while the thermal deformations are caused in the rotor axial, radial and circumferential directions, the thermal deformations, especially the thermal deformation in the rotor radial direction, are sufficiently absorbed by the bellows member and the steam leakage can be prevented by the simple structure.
(11) As an eleventh one of the present invention, in addition to the means of the gas turbine steam passage seal structure of the invention (1), the cooling steam supply passage connection portion at its portion provided in the blade ring steam passage hole is constructed comprising seal pipes provided at upper and lower ends thereof and a bellows member, provided therebetween, that is elongatable and contractible in the rotor radial direction.
(k) By this construction, the same function and effect as in the above item (a) can be obtained. Moreover, the bellows member is provided in the cooling steam supply passage connection portion and the thermal deformations are sufficiently absorbed, like in the above item (j), and the steam leakage can be prevented by the simple structure.
(12) As a twelfth one of the present invention, in addition to the means of the gas turbine steam passage seal structure of the invention (1), the cooling steam supply passage connection portion is constructed comprising a seal pipe and a bellows member connected to each other, the bellows member being elongatable and contractible in the rotor radial direction.
(l) By this construction, the same function and effect as in the above item (a) can be obtained. Moreover, the bellows member is provided in the cooling steam supply passage connection portion and the thermal deformations are sufficiently absorbed, like in the above item (j), and the steam leakage can be prevented by the simple structure.
(13) As a thirteenth one of the present invention, in addition to the means of the gas turbine steam passage seal structure of the invention (1), the cooling steam supply passage connection portion is constructed comprising a plurality of seal pipes, a bellows member, that is elongatable and contractible in the rotor radial direction and is interposed between adjacent ones of the plurality of seal pipes and a bellows member, that is elongatable and contractible in the rotor axial direction and is interposed between other adjacent ones of the plurality of seal pipes.
(m) By this construction, the same function and effect as in the above item (a) can be obtained. Moreover, the two types of the bellows members, one being elongatable and contractible in the rotor radial direction and the other being elongatable and contractible in the rotor axial direction, are provided in the cooling steam supply passage connection portion. Thus, in operation of the gas turbine, while the thermal deformations are caused in the rotor axial, radial and circumferential directions, the thermal deformations in every direction can be sufficiently absorbed by the two types of the bellows members and the steam leakage can be prevented more securely.